The compound (5-Benzyl-3-furyl)methyl 2,2-dimethyl-3-(2-methylpropenyl)cyclopropanecarboxylate which is sometimes written as 5-benzyl-3-furylmethyl chrysanthemate, is more generally known by the generic term Resmethrin. (Either formula name or this generic term may be used interchangeably throughout this specification). This compound is a widely used, broad spectrum insecticide which combines a high insecticidal activity and low mammalian toxicity.
The compound, however, has one significant drawback which has limited its use. The compound is known to give off an unpleasant, urine-like odor after its application. In addition, the oder which is produced is very persistent and remains noticeable for a long period of time, particularly if the compound is used on absorptive surfaces such as rugs, wood paneling or the like.
Conventional odor control methods have been employed to attempt to mask this unpleasant odor. In this regard, perfumed masking agents have been tested, but the masking effect only lasts for a short period of time. The unpleasant odor of Resmethrin typically persists for such a long period of time that any masking effect of such a perfume becomes ineffective.
This unpleasant odor is readily detected after exposure to sunlight, or even bright artificial light. Antioxidants, ultraviolet screening sunscreens, oxidizing and reducing agents have been suggested to prevent light-induced decomposition. Some of these agents have been successful in delaying the on-set of the typical unpleasant, urine-like odor. In this regard, British Specification No. 1,429,437 shows the addition of 2,2'-methylene bis-(6-tert-butyl-4-ethylphenol), known to be an anti-oxidant, to render the odor of Resmethrin less unpleasant. Also disclosed as optional UV-absorbers were 4-tert-butylphenyl salicylate or 2-hydroxy-4-methoxybenzophenone.
The unpleasantness and persistance of this odor has limited the specific uses for which Resmethrin is generally acceptable. Further, these problems have limited the use of Resmethrin in general purpose insecticidal compositions. Such compositions typically contain two or more specific purpose insecticides in combination. For example, such compositions frequently contain synthetic pyrethroids, variously known as Allethrin (the allyl homolog of cinerin I available commercially from Rousell-Uclaf), Bioallethrin (d-transallethrin available commercially from Fairfield American Corp.), Neopynamin (tetramethrin commercially available from Sumitomo), or other pyrethrins, all of which are known to have good "knockdown" activity, and are therefore particularly useful in household sprays for flying insects. Such compounds, when combined with Resmethrin and, preferably, a synergist such as piperonyl butoxide, produce a useful, general purpose House and Garden-type aerosol with good knockdown and killing power. Such compositions would be expected to have a greater general acceptance if the odor problems associated with Resmethrin could be overcome.